Extensive hydrogen and halogen bonding, and absence of intramolecular hydrogen bonding between alcohol and nitro groups in a series ofendo-nitronorbornanol compounds

Abstract

The influence of the substituent at the C2 position on the hydrogen-bonding patterns is compared for a series of five related compounds, namely (±)-3-exo,6-exo-dibromo-5-endo-hydroxy-3-endo-nitrobicyclo[2.2.1]heptane-2-exo-carbonitrile, C(8)H(8)Br(2)N(2)O(3), (II), (±)-3-exo,6-exo-dibromo-6-endo-nitro-5-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol, C(13)H(13)Br(2)NO(3), (III), (±)-methyl 3-exo,6-exo-dibromo-5-endo-hydroxy-3-endo-nitrobicyclo[2.2.1]heptane-2-exo-carboxylate, C(9)H(11)Br(2)NO(5), (IV), (±)-methyl 3-exo,6-exo-dibromo-7-diphenylmethylidene-5-endo-hydroxy-3-endo-nitrobicyclo[2.2.1]heptane-2-exo-carboxylate, C(22)H(19)Br(2)NO(5), (V), and (±)-methyl 3-exo,6-exo-dibromo-5-endo-hydroxy-3-endo-nitro-7-oxabicyclo[2.2.1]heptane-2-exo-carboxylate, C(8)H(9)Br(2)NO(6), (VI). The hydrogen-bonding motif in all five compounds is a chain, formed by O-H...O hydrogen bonds in (III), (IV), (V) and (VI), and by O-H...N hydrogen bonds in (II). All compounds except (III) contain a number of Br...Br and Br...O halogen bonds that connect the chains to each other to form two-dimensional sheets or three-dimensional networks. None of the compounds features intramolecular hydrogen bonding between the alcohol and nitro functional groups, as was found in the related compound (±)-methyl 3-exo,6-exo-dichloro-5-endo-hydroxy-3-endo-nitrobicyclo[2.2.1]heptane-2-exo-carboxylate, (I) [Boeyens, Denner & Michael (1984b). J. Chem. Soc. Perkin Trans. 2, pp. 767-770]. The crystal structure of (V) exhibits whole-molecule disorder.